1. Field of the Invention
The present invention relates to an on-board multibeam radar apparatus, a multibeam radar method, and a multibeam radar program, which can detect a target using a reflected wave from the target in response to a transmitted wave.
2. Background Art
In recent years, on-board detection apparatuses measuring the distance, the relative velocity, and the azimuth between a vehicle and another vehicle (which is also referred to as a reflecting object, an object, or a target) using a millimeter wave radar or the like have been practically used. As on-board radars, an FMCW (Frequency Modulated Continuous Wave) radar, a multi-frequency CW (Continuous Wave) radar, a pulse radar, and the like have been known.
In such on-board radars, a spectrum estimating method using a high-resolution algorithm, such as an AR spectrum estimating method (including a maximum entropy method or a linear prediction method) and a MUSIC (MUltiple SIgnal Classification) method which can achieve a high resolution with a small number of channels, has been used as a signal processing technique of detecting the direction of an arrival wave (a received wave) from a target (a reflecting object) (see JP-A-2009-156582 (Patent Document 1) and Japanese Patent No. 4098311).
Here, a multibeam radar apparatus (also referred to as a beam space system) is known with respect to an electronic scanning radar apparatus of an array antenna system (also referred to as an element space system).
In recent years, dielectric lens antennas have been studied for the multibeam system (for example, see Design of Multibeam Dielectric Lens Antennas by Multiobjective Optimization/IEEE Trans. AP Vol. 57 No. 1, pp. 57-63, 2009, Shizuoka University). Regarding on-board multibeam radar apparatuses, radar apparatuses using a dielectric lens antenna have been developed (for example, see JP-T-2009-541725).
Since the multibeam system represented by a dielectric lens antenna can embody high-gain/high-efficiency antennas more easily than the array antenna system, it is easier to detect a target with a small RCS (Radar Cross Section) even in environments with a low SNR (Signal to Noise Ratio).
Depending on the shape of a lens or the arrangement of primary feeds (primary radiators) and because of no grating lobe occurring, it is possible to flexibly design multibeam radars with various FOVs (Fields Of View) or various gain properties.